Hugs. I wish they get better soon too.
I know what it feels like to have your kitty at the vet. My one cat disappeared for a full long 4 days and she was moody with her tail dropping very straight down when she came home. It wasn't how she usually kept her tail tho, she normally holds it in an s shape.
So my family says "don't worry. It's just because she was away for a while". Naturally the mommy in me didn't believe them and i took her to the vet early the next day. Turns out that she was in a fight and the other cat bit her on her tail, which got infected. I think it's because she was hurt that she came home... But anyhow, she also had her anti biotics and her temperature taken and she wasn't happy at all.
So yeah. I know how it feels like. My kitty loved me soon again afterwards, so don't worry. She still doesn't like the kitty cage tho. *hugs*
I don't know if this will help, but I found that if powder the pills (put the pill in a table spoon and crunch it with a teaspoon worked best for me) and mix it with soft kitty foods (i had Whiskers but i'm not sure where else you can get it), especially ones with a bit of gravy, that they munch that up pretty quick. I couldn't stand to push a pill down my baby's throat.
. They may like the regular soft meals too much tho. Haha.
I hope everything works out for you and the two kitty's. ^_^